Integrated studies to identify site-specific parameters for environmentally benign mining operations: A case study from the Sukari Gold Mine, Egypt

Abstract

This study integrates observations from field and remote sensing data, along with geochemical and isotopic analyses, to assess the environmental impacts of cyanidation and mining activities in the Sukari gold mine (SGM), Eastern Desert, Egypt, in particular, and the orogenic gold deposits of the Arabian-Nubian Shield (ANS) in general. Our findings indicate: (1) groundwater flows south to north in the highly fractured basement aquifer related to the brittle deformation associated with the Najd Fault System; (2) massive gabbroic bodies separate the fractured basement aquifer into east and west conduits; (3) the tailings storage facility (TSF) pond and leach pad were constructed over the west conduit; and (4) cyanide-rich wastewater has leaked downward through tears and cuts in the lining of the TSF pond into the fractured aquifer and cyanide contaminants have migrated northward along the west conduit. Evidence for the latter includes: (1) toxic concentrations of cyanide (total: 0.018–9.4 mg/L; free weak-acid dissociable: 0.003–0.7 mg/L) were observed in groundwater samples north of the TSF pond; (2) similarities in electrical conductivity (EC) values and chloride/bromide (Cl−/Br−) ratios between groundwater north of the pond (EC: 88.8 mS/cm; Cl−/Br−: 346 to 363) and those of the TSF pond water (mean EC: 99 mS/cm; Cl−/Br−: 242 to 383) were observed; (3) the geochemical (e.g., sodium [Na+], Cl−) and isotopic compositions (δ18O and δ2H values) of groundwater are consistent with mixing of groundwater upgradient from the SGM with isotopically enriched pond water; and (4) cyanide contamination could not have resulted from an overflow of the TSF pond during flash flood events, given that rainfall is negligible and effective flood control systems are in place. Our findings show that the international codes/regulations do not fully address site-specific characteristics and highlight the importance of considering these parameters in mining of orogenic gold deposits in the ANS.